1. Field of the Invention
The present invention relates generally to the design of a time-to-digital converter, and more particularly to a hybrid coarse-fine time-to-digital converter.
2. Description of the Background Art
A time-to-digital converter is usually employed to measure the time difference of two input signals. The performance of a time-to-digital converter is characterized by its linearity, offset, and resolution. The finer resolution results in a much smaller quantization noise in any application. A coarse time-to-digital converter usually has very small offset and better linearity while its quantization resolution is generally much larger. Though a fine time-to-digital converter results in a smaller quantization noise, it has a comparably large offset and worse linearity, which are quite sensitive to process, voltage, and temperature variations.
To achieve a finer quantization resolution, a low offset, and a good linearity, a hybrid coarse-fine time-to-digital converter is proposed in the invention.